1. Field of the Invention
The invention relates to an image sensor structure, and more particularly to an image sensor structure with an array of protrusions disposed between bond pads and a sensing area.
2. Description of the Related Art
An image sensor, as a kind of semiconductor device, transforms optical images into electrical signals. Image sensors can be generally classified into charge coupled devices (CCDs) and complementary metal oxide semiconductor (CMOS) image sensors. Among these image sensors, a CMOS image sensor comprises a photodiode for detecting incident light and transforming it into electrical signals, and logic circuits for transmitting and processing the electrical signals.
In the process for fabricating an image sensor, multiple photoresist coating processes in various stages are required. However, non-uniform photoresist coating generally occurs due to an uneven wafer surface having trenches with various depths for subsequently forming, for example, bond pads and scribe lines, resulting in the formation of striation defects on the wafer, deteriorating the display picture quality.
Currently, a technique of filling photoresist material into the trenches with various depths to even the wafer surface before the above-mentioned photoresist coating process has been adopted to reduce striation defects. However, in order to fill the trenches with various depths, multiple masks are required, thus increasing cost.
Therefore, development of method which can effectively solve the striation defect issue is desirable.